The present invention relates to pharmaceutical preparations having a drug-ion exchange resin complex that is treated to provide programmable release characteristics in the gastrointestinal tract.
One important aspect of drug therapy is the effect of a drug for an extended time and in many cases, the longer the time, the more substantial the benefit.
Use of ion-exchange resins to form a drug-ion exchange resin complex is well known and is described, for example, in U.S. Pat. No. 2,990,332. In this patent, the use of an ion-exchange resin to form a complex with ionic drugs and thereby delay the drug release from such complexes is described. Such delay in drug release was deemed to be of relatively short duration. Since then there have been additional publications and patents (e.g., U.S. Pat. Nos. 3,138,525; 3,499,960; 3,594,470; Belgian Patent No. 729,827; German Patent No. 2,246,037) that describe use of such ion-exchange resin complexes with water-permeable diffusion barrier coatings of the drug-ion exchange resin complex coated to alter the release of drugs from the drug-ion exchange resin complex.
Sustained or prolonged release dosage forms of various drugs are known and commercially available. However, there are only a few products available that provide sustained release of the drug from the very fine particles of coated drug-ion exchange complexes. A recent US Published Patent Application No. US 2005/0181050 A1, published Aug. 18, 2005, mentions that few modified release liquids containing drug-loaded ion exchange resin particles are commercially available. It further states that such products require several time consuming steps and require the use of a potentially hazardous step of coating from a solvent based solution. The regulatory authorities require that such solvents are thoroughly removed from the pharmaceutical products before ingestion.
Raghunathan in U.S. Pat. Nos. 4,221,778; 4,847,077 and Raghunathan et al. in J. Pharm. Sci., Vol 70, pp 379-384, April 1981, describe treating drug-ion exchange resin complexes with water soluble, hydrophilic impregnating (solvating) agents such as polyethylene glycol and others so as to enable the coating of drug-ion exchange resin complexes with a water-permeable diffusion barrier. These publications indicate that the drug-ion exchange resin tended to swell when in contact with water, causing the coating layer to fracture and prematurely release the drug thereby adversely impacting the purpose of the coating (i.e., control release). Attempts to minimize such rupture of the coating layer were made using impregnating (solvating) agents to control the swelling of the drug-ion exchange resin complex. Other patents describing variations of this type of product are referenced in US Published Patent Application No. 2003/0099711 A1, section 0006.
Further, Kelleher et al. in U.S. Pat. No. 4,996,047 describe using a drug content above a specified value in the drug-ion exchange resin complex to avoid the swelling of the drug-ion exchange resin complex and thereby minimizing the rupture of the coating. Umemoto et al., describe in U.S. Pat. No. 5,368,852 that despite the use of impregnating agents, certain preservatives used in the liquid preparation tend to cause the rupture of the diffusion barrier coating of the drug-ion exchange resin complex. Umemoto et al. reported overcoming the rupture of the coating membrane by use of a preservative that did not cause the rupture.
Another patent, U.S. Pat. No. 6,001,392 granted Dec. 14, 1999 describes certain acrylate based (e.g., EUDRAGIT polymer system) and ethyl cellulose (e.g., SURELEASE, AQUACOAT) polymers for coating a drug-ion exchange resin complex using either a solvent or aqueous based coating to achieve sustained release of the drug from the drug-ion exchange resin complex. No meaningful data is disclosed regarding the integrity of the coating film. Further, there is no reported data or evidence of prolonged release of the drug from the coated drug-ion exchange resin complex beyond about 12 hours. A more recently Published Patent Application No. US 2003/0099711 A1, describes using an ethyl cellulose polymer in an aqueous based coating system. This publication further describes use of an enteric coating as an optional added coating to delay the drug release. There have been literature-reported drawbacks of using ethyl cellulose based aqueous dispersions as coatings for drug-ion exchange resin complexes.
Similarly, there have been drawbacks associated with previously used polymers of acrylate and methacrylate-based aqueous dispersion coating systems for coating drug-ion exchange resin complex. Amongst these shortcomings observed is significant tackiness upon application of the coating and during curing, which complicates the coating process of drug-ion exchange resin complexes and/or requires the addition of further components such as an anti-tacking material to counteract this undesirable property.